A variety of materials and assembly methods have been used throughout history to construct roofing. Many of these building materials carry along significant disadvantages in areas such as reliability, longevity, maintenance and installation costs. There have also been significant issues associated with how these roofing materials are assembled to form a complete roof.
Natural slates have been used in roofing for centuries and can last for 50 to 100 years or more. Natural slates require vertical overlapping so the exposed part of each slate is often less than one-half the total length of the original slate piece. Such overlapping results in a roof that is heavy, often reaching weights in excess of 20 pounds per square foot. For a roofing square of a 10 by 10 foot section of roof, weights may reach around 2000 pounds per roofing square. Natural slate is expensive to purchase, difficult to install and is too heavy for most roofs on homes build today. Natural slates are difficult to manufacture and are typically narrow compared to their vertical dimension. Installers are constantly challenged by small pieces which are needed at roof areas such as hips, rakes and valleys. Many of these pieces must be fasted by special means such as custom hooks, custom hangers, specially tied wires or nails driven near areas requiring special waterproofing. These custom areas require specialized skilled labor by installers and are highly time consuming, driving up installation costs for builders.
Natural wood shingles or thicker, heavier wood shakes are expensive and sometimes require special roof construction so as to allow the roof structure to breathe. Wood roofs can have problems with algae and rot. They also can represent a significant fire hazard. This is especially true in areas with wildfires. Wood shingles and shakes are difficult to maintain in hot, dry climates. These climates can cause the wood to become brittle, crack, and become vulnerable to meteorological conditions like hail and high winds.
Clay or concrete tile roofs are heavy and often require special reinforcements so as not to collapse the roof structure. Typical clay and concrete tiles are known to absorb water, sometimes more than 3 percent by weight. This causes problems in climates that experience freezing temperatures. When absorbed water freezes, the water expands, resulting in tiles that crack and fail. This results in a short life of the roof, requiring more frequent replacement. Clay and concrete tiles often have overlapping or interlocking top and side edges. If these are damaged during installation, roof leaks can often result. These leaks are often not detected until after the roofer has left the job site. Most tile roofs require elevated wooden battens which run horizontally along the roof. These battens are usually wooden pieces such as the one by twos which are nailed flat to the roof. If a tile fails or cracks, water can penetrate to the roofing felt layer and the batten causes a dam. This built up water accumulates and can run sideways until it finds a way inside the house, typically through a nail hole. Costly water damage is the end result.
Synthetic roofing products have been developed to simulate natural material roofs such as slate or wood. Typical synthetic roofing products include cementitious, plastic, rubber, fiberglass and other composite materials. Each of these prior art synthetics has been associated with problems such as color fading, cracking, curling, peeling and other conditions which shorten the life of the roof.
Most roofing tiles and slates require nails to be driven through the product or through nail holes provided in the tiles or slates. During installation, the installer may over drive the nails resulting in a broken or damaged tile. Conversely, if the nail is under driven, a raised nail head may create a stress point on the tile above it, resulting in the tile breaking.
Natural roofing products and tiles are typically individual, narrow pieces which take time to install and fasten. These products have a joint line between each narrow, individual piece which increases the likelihood of water penetration and infiltration to the roof deck and the structure below.
Prior art roofing panels are generally designed with tongue-and-groove type design or otherwise side overlapped to accommodate water channeling between panels along their side edges. In order for the channel to be durable enough to withstand handling during installation and environmental stresses, the tile must be of increased thickness resulting in an increase of product weight on the roof. This increased thickness also reduces the architectural simulations the tile may intend. Other prior art materials include metal or steel which is stamped to include side locking channels but are limited in their intended architectural replications.
Prior art staggered length roofing products require the installer to measure and fasten each roofing piece individually to vary the length. This method is time consuming and results in high installation costs. Hangers and battens have been used to hold roofing pieces however staggered roofing pieces require that individual hangers be swapped out one by one to accommodate the different length pieces. Multiple hangers of varying sizes are required. Also hangers have been known to slip loose under conditions of high weight on the roof surface such as during high snowfall or icing events.